%0 Journal Article
%T Amyloid Beta Peptide Slows Down Sensory-Induced Hippocampal Oscillations
%A Fernando Peˋa-Ortega
%A Ram車n Bernal-Pedraza
%J International Journal of Peptides
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/236289
%X Alzheimer＊s disease (AD) progresses with a deterioration of hippocampal function that is likely induced by amyloid beta (A汕) oligomers. Hippocampal function is strongly dependent on theta rhythm, and disruptions in this rhythm have been related to the reduction of cognitive performance in AD. Accordingly, both AD patients and AD-transgenic mice show an increase in theta rhythm at rest but a reduction in cognitive-induced theta rhythm. We have previously found that monomers of the short sequence of A汕 (peptide 25每35) reduce sensory-induced theta oscillations. However, considering on the one hand that different A汕 sequences differentially affect hippocampal oscillations and on the other hand that A汕 oligomers seem to be responsible for the cognitive decline observed in AD, here we aimed to explore the effect of A汕 oligomers on sensory-induced theta rhythm. Our results show that intracisternal injection of A汕1每42 oligomers, which has no significant effect on spontaneous hippocampal activity, disrupts the induction of theta rhythm upon sensory stimulation. Instead of increasing the power in the theta band, the hippocampus of A汕-treated animals responds to sensory stimulation (tail pinch) with an increase in lower frequencies. These findings demonstrate that A汕 alters induced theta rhythm, providing an in vivo model to test for therapeutic approaches to overcome A汕-induced hippocampal and cognitive dysfunctions. 1. Introduction Alzheimer＊s disease (AD), the most common form of dementia, is characterized by a progressive decline in cognitive function [1每5] that correlates with the extracellular accumulation of amyloid beta protein (A汕) [1, 4, 5]. Deterioration of hippocampal function, likely induced by A汕 oligomers, contributes to the memory deficits associated with Alzheimer＊s disease (AD) [5每8]. Normal hippocampal function is strongly dependent on a 3 to 10 Hz oscillatory activity, namely, the theta rhythm [9每11]. Theta oscillations have been associated with various cognitive processes in several species, including humans [9每11]. Theta rhythm abnormalities are usually related to memory deficits and pathological changes in the brain [12每14]. In fact, subjects with AD show a typical ※electroencephalographic slowing§ that includes increased slow rhythms and decreased fast rhythms [6, 13, 15, 16]. Regarding theta rhythm, AD patients show increased theta rhythm at rest [6, 15, 16], but they also show a decrease in induced-theta rhythm; both of these changes in theta rhythm correlate with a reduced cognitive performance [17]. A similar contradictory scenario has
%U http://www.hindawi.com/journals/ijpep/2012/236289/